1. Field of the Invention
The present invention is related generally to steam turbines, and more particularly to an improved apparatus and method of fabricating same which provides integrated casing alignment and steam extraction for retrofit inner cylinders in such steam turbines.
2. Statement of the Prior Art
In prior art steam turbines, for example, those steam turbines which were manufactured by Westinghouse Electric Corporation and predated the "BB" (i.e., building block) era, the original inner cylinders or casings were most often made of cast iron or cast grey iron, and sometimes cast steel. These casing designs of such older steam turbines had a bulky, costly and rather elaborate manifold structure, incorporated in the inner cylinder base, which routed not only the extraction steam flow, but also moisture removal flow in the cases of "non-reheat" units, from both ends of a double flow low pressure blade path to a single chamber to which the extraction steam piping or moisture removal vent piping was connected.
These known manifold structures also contained lugs at each end and at each side in order to accommodate for alignment loads between the outer and inner cylinders of the turbine. Most typically, such alignment loads could occur due to differential friction, pressure imbalance, inlet piping reactions, and other disturbances including seismic events. As a result, the above described cast construction most readily accommodated the complex shapes that were necessitated by the known manifold structures.
It has since been discovered that the original inner casings of such steam turbines also did not remove a sufficient amount of moisture from their blade paths. This remaining moisture, in turn, lead to heavy erosion damage both to the stationary parts of the turbine and to the rotating parts thereof. Such damage necessitated costly repairs and often required the use of stainless steel liners throughout the damaged turbines' blade path.